The present invention generally relates to packaging and more particularly is directed to a rotating stretch wrapping apparatus for making unitary packages which incorporates a linear traveling clamping and cutting assembly.
Case packing or boxing is a common way of shipping multiple unit products. Multiple unit products are generally stacked in a corrugated box or are wrapped with kraft paper with the ends of the kraft paper being glued or taped.
Some manufacturers use strapping of vertical steel or plastic binding to unitize the product. The problems incurred in the use of strapping are the requirement of costly corner protectors, danger of bending or snapping and injury to the operator while applying this high tension material to the loads and the ever present problem of product settling due to moisture wetting the cartons, carton sides bulging or normal vibrations causing the straps to loosen and the load to come apart.
Glue is an alternative method used in some areas but customer dissatisfaction with gluing is high because removal of glued cartons or bags from the unitized loads tends to tear outside layers of the cartons. Glue, although an inexpensive material, demands interleaving for product orientation requiring more durable and expensive packaging material.
Tape, another alternative method of packaging, is currently being used to horizontally bind the top layer of the load. However, tape is expensive and allows relatively free movement of all product surrounded.
Another method of wrapping products is by putting a sleeve or covering of heat shrinkable material around the products and shrinking the sleeve to form a unitized package. The use of heat shrinkable film is described in U.S. Pat. Nos. 3,793,798; 3,626,645; 3,590,549 and 3,514,920. A discussion of this art is set forth in U.S. Pat. No. 3,867,806.
A rapidly growing economical way of packaging products is by wrapping the product load with a web of stretched plastic film.
The elasticity of the web of stretched plastic film holds the products of the load under more tension than either shrink wrap or kraft wrap, particularly with products which settle after packaging. The effectiveness of stretched plastic film in holding a load together is a function of the containment or stretch force being placed on the load and the ultimate strength of the total layered film wrap. These two functions are determined by the modulus or hardness of the film after stretch has occurred and the ultimate strength of the film after application. Containment force is currently achieved by maximizing elongation until just below a critical point where breaking of the film occurs. Virtually all stretch films on the market today including products of Mobil Chemical Company (Mobil-X, Mobil-C, Mobil-H), Borden Resinite Division PS-26, Consolidated Thermoplastics, Presto, PPD and others are consistently stretched significantly less than capacity because of irregularities in film brake systems. These systems depend upon friction induced drag either directly on the film through a bar assembly or indirectly as is shown in U.S. Pat. Nos. 3,867,806 and 4,077,179.
The use of wrapping machinery to wrap stretched film around a load is well known in the art. Four types of stretch wrapping apparatus are commonly used in the packaging industry and these types are generally described as spiral rotary machines, full web rotary machines, pass-through machines, and circular rotating machines.
An example of a spiral machine is shown in U.S. Pat. No. 3,863,425 in which film is guided from a roll and wrapped around a cylindrical load in a spiral configuration. A carriage drives the film roll adjacent the surface of the load to deposit a spiral wrap around the load and returns in the opposite direction to deposit another spiral overwrap around the load.
In U.S. Pat. No. 3,788,199, tapes are spirally wound in such a manner that they overlap each other to provide suitable space therebetween when breatheability is required. In this disclosure, a heavy duty bag is prepared by spirally winding stretched tapes of synthetic resin in opposite directions, so that they intersect each other to form a plurality of superimposed cylindrical bodies which are bonded together to form a cylindrical network. The spirally wound inner and outer tapes of the superimposed cylindrical body intersect each other at a suitable angle, depending upon the application intended, the preferred embodiment having substantially equal longitudinal transfer strength. In this preferred embodiment, the tapes intersect each other at an angle of about 90.degree.. The angle defined by the tapes constituting the cylindrical network may be determined by varying the interrelationship between the traveling speed of the endless belts carrying the tape and the rotating speed of the bobbin holders, which rotate a plurality of tape bobbins to deposit the tape onto the moveable belt.
Spiral wrapping machines which are currently commercially available are manufactured by Lantech, Inc., under Model Nos. SVS-80, SVSM-80, STVS-80, STVSM-80 and SAHS-80.
A full web type of apparatus which wraps stretched film around a rotating load is disclosed in U.S. Pat. No. 3,867,806 assigned to Lantech, Inc. A similar full web apparatus using a tensioned cling film wrapped around a rotating load is shown by U.S. Pat. No. 3,986,611 while another apparatus using a tacky PVC film is disclosed in U.S. Pat. No. 3,795,086.
Full web wrapping machines typical of those presently commercially available are Model Nos. S-65, T-65 and SAH-70 manufactured by Lantech, Inc.
Another type of machine for wrapping a pallet load commonly called a pass-through machine is disclosed in U.S. Pat. No. 3,596,434. In this reference, a pallet load is transported along a conveyor and the leading face of the pallet load contacts a vertical curtain of film formed by the sealed leading edges of film webs dispensed by two rolls of film on opposite sides of the path of the pallet load. The pallet load continues to move along the conveyor, carrying with it the sealed film curtain until the two side faces of the pallet load as well as the front face are covered by film web. A pair of clamping jaws then close behind the pallet load, bringing the two film web portions trailing from the side faces of the pallet load into contact with one another behind the pallet. The jaws then seal the film web portions together along two vertical lines, and cut the web portions between those two seals. Thus, the film web portions are connected to cover the trailing face of the pallet load, and the film curtain across the conveyor is re-established to receive the next pallet load. The pallet load may subsequently be exposed to heat in order to shrink the film web and apply unitizing tension to the load, as is disclosed in U.S. Pat. No. 3,662,512. Another disclosure of relevance to pass-through wrapping is U.S. Pat. No. 3,640,048 which shows that film may be applied to the top and bottom of the pallet load prior to the wrapping cycle when it is desired to cover all six surfaces of the pallet load with film. Commercial pass-through machines are currently manufactured by Weldotron Corporation.
Various apparatus and processes have been developed to rotatably wrap stacked components to form a load.
Devices in which stationary loads are brought to a loading area and are wrapped by a rotating member which dispenses stretched film around a load are disclosed in U.S. Pat. Nos. 4,079,565 and 4,109,445. U.S. Pat. No. 4,079,565 discloses a full web vertical wrap of the load while U.S. Pat. No. 4,109,445 discloses the horizontal spiral wrap of a load. U.S. Pat. No. 4,050,220 discloses a wrapping device for multiple unit loads. Each load is conveyed to a wrapping area in which a load is supported on one or more stationary planar surfaces. The leading edge of a roll of stretchable plastic wrapping material is held adjacent to the load, and the roll of material is rotated about the load and the supporting surfaces, wrapping the load and the supporting surfaces together. The plastic wrapping material is stretched during the wrapping operation so that the material is under tension when applied to the load. After the wrapping cycle is complete, the load is pushed past the ends of the supporting surfaces, and the wrapping material which covered the supporting surfaces collapses against the sides of the load. Further developments of this wrapping system are disclosed in U.S. Pat. Nos. 4,110,957 and 4,178,734.
U.S. Pat. No. 603,585 discloses a spiral wrapping device for enclosing individual newspapers in paper wrap for mailing purposes. Each newspaper is placed on a cylindrical core with a circumference approximately twice that of a newspaper, and each newspaper advances along the length of the core as the core is rotated. Wrapping paper is applied to the core at an angle and the wrapping paper between newspapers is severed as each newspaper reaches the end of the cylinder and is placed on a flat horizontal surface, thereby collapsing the wrapping paper against the underside of the newspaper previously pressed to the cylinder.
U.S. Pat. No. 1,417,591 discloses a wrapping machine for individual items such as boxes in which each item is conveyed along the surface of a horizontal sheet of wrapping material. The edges of wrapping material on each side of the item are curled upward to meet one another atop the item to be wrapped thereby forming a tube around the item. The leading end of the tube is sealed and the trailing end of the tube is severed and then sealed to enclose the item. Another device which utilizes this system of wrapping is disclosed in U.S. Pat. No. 3,473,288.
In U.S. Pat. No. 2,575,467, a wrapper of cylindrical packages for material such as sausage is disclosed in which the package is rotated about its cylindrical axis as wrapping tape is applied to an angle to form a cylindrical wrap.
In U.S. Pat. No. 2,863,270, two cylindrical items of approximately equal diameter are abutted at their planar ends, and placed by hand in a cradle which exposes the complete circumference of the abutting ends. A roll of wrapping material is then driven by a hand crank mechanism to circulate around the circumference of the abutting ends, applying wrapping material thereto. When sealed together, the pair of cylindrical items are removed from the cradle by hand.
A spiral wrapping machine for long bundles of items such as filaments is disclosed in U.S. Pat. No. 3,000,167. As the bundle of filaments moves along its axis through the wrapping area, a ring circulates about the bundle carrying a roll of wrapping material which is applied to the bundle to form a spiral wrap. Because the normal load of filaments or similar items is much longer than the wrapping area, it is not necessary to provide support for the bundle in the wrapping area.
Commercial circular rotating wrapping machines are presently manufactured by Lantech, Inc., under the trademark LANRINGER and are provided with wrapping ring inner diameters of 36 inches, 54 inches, 72 inches and 84 inches. In differentiating between the various circular rotating wrapping machines manufactured by Lantech, Inc., the manual model has the designation SR; the full web models have the designations SVR and SAVR; the multiple banding models have the designation SVBR and SAVBR; the spiral models have the designation SVSR and SAVSR and the continuous wrap or bundler models have the model designation SVCR and SAVCR.
One method of severing and sealing the film web at the end of the wrapping cycle is illustrated in U.S. Pat. No. 4,317,322 assigned to Lantech, Inc. In this reference, a pair of rotating clamp jaws are mounted beneath the wrapping conveyor, and a positioning and cutting assembly is pivotably mounted to swing into an area between the closed clamp jaws and the conveyor on the same side of the ring as the film supply. The positioning and cutting mechanism is driven upwards by a fluid cylinder and engages the film web angled between the edge of the conveyor and the film web supply roll mounted on the ring beneath the clamp jaws. The leading edge of the positioning and cutting mechanism engages the film web and carries it into position directly underneath the conveyor so that the web extends downward from the positioning and cutting mechanism to the supply roll through the area in which the clamp jaws will close. The clamp jaws are then activated to close and hold the film web between the positioning and cutting assembly and the roll. The positioning and cutting assembly includes a cutting edge mounted to a second fluid cylinder, the second cylinder being adapted to drive the cutting edge forward to sever the web after the jaws are activated to clamp and hold the web. A brush is also mounted to the positioning and cutting assembly and is directed upwards to brush the upper portion of the engaged film web against the underside of the conveyor and the prior layers of web wrapped there. The tackiness of the plastic film web holds the upper portion against the underlying layers and creates a commercially viable seal. The lower severed portion of the film web is held by the clamp jaws and extends from the jaws to the film roll. The positioning and cutting assembly is then pivoted out of the wrapping area, and the conveyor is activated to transport the load out of the wrapping area. Subsequently, another load may be delivered to the wrapping conveyor in the wrapping area, and the film web roll may be carried around the load and conveyor through at least one complete revolution. The clamp jaws are then rotated apart to release the severed end of film web, and the stretched tensioned web collapses against the underside of the conveyor.
The above described system suffers from a number of deficiencies. The system requires exact stopping of the roll in a specific position and, thus, deceleration of the ring and mounted roll takes a significant amount of time. Once the roll is stopped, the cutter arm is brought up from the bottom and the time involved for severing each wrapped package ranges from five (5) to ten (10) seconds a time consuming process. The film web roll must be mounted entirely on one side of a rotating ring apparatus which encircles the wrapping area, so that the width of film web does not extend through the ring plane. This is made necessary by the need to sever the entire width of film web between the clamps and the conveyor, as the pivotable positioning and cutting assembly cannot rise up through the ring plane to contact and cut the entire width of film web on both sides of the rotating ring. Thus, the shaft which carries the film web on the ring is subject to moment forces during stretching of the film web, and has a limited span of usefulness. Moreover, the positioning and cutting apparatus is energy inefficient in requiring the transportation of a substantial mechanical mass through a long arc. Control and power for the cutting edge cylinder must likewise be transported, which increases the complexity and number of moving parts inherent in the apparatus. Furthermore, the positioning and cutting apparatus must arrive at a precise location within the wrapping area in order to perform its purpose effectively, and the precise tolerances required of the fluid cylinder pivoting system increase the cost of the apparatus.
Therefore, it is clear that there exists a need in the art for a more energy-efficient, simplified and accurate mechanism for the clamping, cutting and brushing of film web at the end and beginning of each wrap cycle. Such a mechanism should preferably allow the film web roll to be mounted across the plane of the rotating ring, so as to reduce shear forces on the film roll shaft. The mechanism must therefore engage the width of the film web through the plane of the rotating ring, and not be limited to action only on one side of the ring.